Natural killer lymphocytes can lyse a wide variety of tumor cells and normal cells. The lysis of target cells by natural killer (NK) cells occurs following binding to target cells. The target structure for NK cells (NK-Tg) and its receptor (NK-R) have not been identified. Present studies are intended to determine, by direct biochemical analysis, the nature of NK-Tg and NK-R. We will consider the following two possibilities: (1) whether the NK-Tg structure is a glycan of glycoliid (GL) and/or glycoprotein (GP), which interacts with a carbohydrate binding NK-R; and (2) conversely, whether NK-Tg is a carbohydrate binding protein which interacts with specific glycans on the surface NK cells. For these studies, we will use a NK-sensitive mouse lymphome cell line, contrasted with NK-insensitive variants as target cells, and purified splenic NK-cells and cloned continuous NK-cell line in separate studies, as effector cells. Our studies will include: (1) differential identification of radiolabeled NK-Tg molecule and NK-R by their binding affinity to intact NK-cells and target cells respectively; (2) radioactive cell surface labeling of target cells, formation of NK-tumor cell doublets, enrichment of these conjugates, chemical cross linking of NK-Tg and NK-R by reversible bifunctional crosslinking agent, immunoprecipitation of crosslinked NK-Tg-NK-R complex, and identification of reactive species (glycoprotein, protein and glycolipid) by gel electrophoresis and thin layer chromatography; (3) identification of NK-R and NK-Tg for their reactivity with known antibodies to NK-cell and lymphoma cell surface markers; and (4) demonstration of the ability of isolated NK-Tg and NK-R to block NK-Tg cell binding and/or lysis. These studies will yield biochemical information regarding the nature of NK-Tg interacting molecules and the role of terminal carbohydrate moieties in the molecular interaction relevant to NK-cell function. (SR)